农用抗生素产生菌菌种选育的研究进展

农用抗生素产生菌的原始菌株 ,往往产量很低或质量较差 ,不能满足工业生产的需要 ,必须对它的某些性状进行改良。改良菌种的主要手段是通过育种 ,筛选出高产菌株。传统的诱变育种是最广泛的选育方法 ,以基因工程为核心的现代生物技术也应用于农用抗生素产生菌的菌种选育中 ,并逐渐成为农用抗生素菌种选育的主导技术。     

原生质体融合技术在微生物菌种选育中的应用

对原生质体融合技术在提高抗生素生产效价,酵母菌工程菌株的构建、多功能菌株的选育以及污水处理工程菌的构建等方面的研究情况进行了综述。     

纳他霉素及其生产菌育种研究进展

纳他霉素是一种高效、广谱、安全的抗真菌天然产物,广泛用做食品防腐添加剂和医用抗菌剂,对植物病原真菌也有强烈抑制作用。由于其主要通过褐黄孢链霉菌等发酵生产,因此高产菌种的选育是纳他霉素研究的热点之一。介绍了纳他霉素的主要理化性质、抑菌特性及其在不同领域的应用,综述了其生产菌育种研究进展,并对不同的育种方法进行了简要的比较分析,探讨了纳他霉素高产菌种选育的发展前景。     

抗生素产生菌诱变育种的研究进展

一种抗生素能否产业化决定于抗生素产生菌菌种的产素水平。因而如何提高抗生素产生菌的产素水平成为抗生素研究工作者长期不懈探索的重要课题。其中,诱变育种以其技术设备简单、省时省力等优点得到了微生物育种工作者的青睐,在诱变育种技术上取得了巨大进展,为抗生素工业化生产发挥了重要作用。综述了抗生素产生菌的诱变育种研究进展。     

原生质体紫外诱变选育灵芝新菌种的研究

对灵芝原生质体进行了紫外诱变处理 ,经过粗筛和精筛后 ,从中选出多糖含量和产量明显高于原始菌株的两株诱变株 430 2 0 #和 430 2 6#。经过 1 0代PDA斜面继代培养及其摇瓶试验和连续 3次 3t罐的中试试验 ,表明所得诱变株为比原始菌株更优秀的稳定高产、高多糖含量的灵芝生产菌株。本研究为选育适合发酵的灵芝生产菌种提供了一种快速、有效的方法     

空间诱变在微生物菌种选育上的研究进展

空间诱变是一种新型有效的微生物育种手段。本主要综述国内外微生物空间条件诱发微生物突变的特点、生物学、细胞学、当代生理损伤效应、突变的机理以及育种中已取得的进展,并提出了存在的问题和今后研究的发展方向。     

微生物菌种改良筛选新技术研究进展

从自然界筛选出来的微生物菌株往往活性比较低,耐受性比较差,不能满足工业化生产的要求.而采用新颖的诱变技术,如微波、离子注入、原生质体诱变和原生质体融合、基因工程技术等能有效改良菌种,提高菌种的活性,降低生产成本,满足工业化生产的要求.同时,构建一种简单易行的改良路线和快速有效的筛选模式是菌种改良选育的关键.     

广西龙眼种质资源研究及品种选育

本文概述广西龙眼种质资源的特点,综述广西龙眼种质资源调查、亲缘关系研究和引种、品种选育进展,并提出进一步开展研究利用的建议.     

Comparison of melibiose utilizing baker's yeast strains produced by genetic engineering and classical breeding

Yeast strains currently used in the baking industry cannot fully utilize the trisaccharide raffinose found in beet molasses due to the absence of melibiase (alpha-galactosidase) activity. To overcome this deficiency, the MEL1 gene encoding melibiase enzyme was introduced into baker's yeast by both classical breeding and recombinant DNA technology. Both types of yeast strains were capable of vigorous fermentation in the presence of high levels of sucrose, making them suitable for the rapidly developing Asian markets where high levels of sugar are used in bread manufacture. Melibiase expression appeared to be dosage-dependent, with relatively low expression sufficient for complete melibiose utilization in a model fermentation system.     

Identification of Rhizobium strains on antibiotic concentration gradients

Antibiotic concentration gradients were used to characterise several cultures of R. phaseoli and Rhizobium spp. (isolated from Cicer arietinum) by differences in intrinsic antibiotic resistance (IAR). Differentiation between cultures was facilitated by use of cluster analyses. The method permitted 15/16 cultures of R. phaseoli to be distinguished on 14 antibiotics. Two cultures which exhibited similar IAR patterns were shown to be the same strain obtained from different collections. The validity of the technique for strain identification was demonstrated by fluorescent antibody tests which gave corresponding identity for 50 nodule isolates from plants inoculated with a mixture of three strains of R. phaseoli. The method was less suitable for characterising cultures of the slow-growing Rhizobium spp. because several antibiotics produced growth lacking a clearly defined boundary between resistance and susceptibility. Although 15/16 cultures of Rhizobium spp. could be differentiated, several isolates were distinguishable only by a difference on a single antibiotic. Similarity between stock cultures and derivative nodule isolates indicated that IAR on gradient plates was a stable property unaffected by plant passage.     

Progress in grapevine breeding

Summary The European, or bunch grape, Vitis vinifera, is widely grown because of its high fruit quality and its capacity to grow in a wide range of climatic conditions. However, they are susceptible to fungal diseases and insect pests, especially when grown in cool, wet climates. The aim of a number of grapevine breeding programs throughout the world is to develop new varieties resistant to diseases using complex hybrids between European and American species of Vitis. Within these breeding programs it is essential to maintain heterozygosity and desirable hybrids are multiplied by asexual propagation. New approaches to grapevine improvement include the use of protoplast fusion to overcome sexual barriers, however the routine regeneration of plantlets from protoplasts and calluses is difficult. In vitro rescue of ovules from varieties with stenospermocarpic seeds shows considerable promise for breeding new seedless grapes. Eventually the use of plant transformation techniques to insert specific pieces of DNA coding for desirable genetic characteristics will provide opportunities for equipping well known grape cultivars with new characteristics.     

A new antifungal antibiotic produced byStreptomyces galbus

A streptomycete producing an antibiotic having antifungal and antibacterial activity was isolated from a soil sample of West Bengal. It was characterized and identified as Streptomyces galbus. The antibiotic was isolated from the fermented broth by treatment with activated charcoal and purified by chromatography on alumina and paper. It is a colourless, odourless, hygroscopic, amorphous compound. Although homogeneous by paper and thin-layer chromatography, the possibility of the presence of two components was indicated by gel filtration. Its physico-chemical characteristics and UV-absorption spectrum suggest a non-polyenic nature. It is active against a wide variety of fungi and bacteria. It has some phytotoxic effect, but is relatively non-toxic to rats.     

Progress on breeding for best-hybridized crossing of meat rabbits

Best-hybridized crossing should ideally result in optimal exploitation of heterosis of lines and capitalize on expressed heterosis. Rabbit breeding is heading in the direction of breeding for best-hybridized crossing of meat rabbits. Most special sire lines are selected for post-weaning average daily gain and marketing weight. Post-weaning growth has a negative and favorable genetic correlation with the feed conversion ratio, which is used in indirect selection for feed conversion ratio. The most common selection criteria for special maternal lines are related to litter size at birth or at weaning. Since the heritability of most reproductive traits is low, we must collect as many individual and relative records as possible in the genetic evaluation of rabbits. The BLUP procedure under an animal repeatability model is the most common procedure used for evaluation of animals in selection programs for special lines of meat rabbits. Direct selection for litter size is less efficient than selection for post-weaning growth, but the estimation of heterosis is generally higher for litter size than that for the post-weaning growth. Evaluation of heterosis could be performed by estimating crossbreeding parameters in the cross or comparing contemporary productivity among purebreds and crossbreds. Here, we reviewed breeding of special lines, exploitation of heterosis of crossbreds, and establishment of crossbreeding system of hybrid meat rabbits and summarized the methodologies of breeding special lines, criteria in selection programs, and the result of heterosis estimates.